1. Field of the Invention
The present invention generally relates to fire-rated building structures. In particular, the present invention relates to fire-rated joint systems, wall assemblies, and other building structures that incorporate the fire-rated joint systems.
2. Description of the Related Art
Fire-rated construction components and assemblies are commonly used in the construction industry. These components and assemblies are aimed at preventing fire, heat, and smoke from leaving one room or other portion of a building and entering another room or portion of a building. The fire, heat or smoke usually moves between rooms through vents, joints in walls, or other openings. The fire-rated components often incorporate fire-retardant materials which substantially block the path of the fire, heat or smoke for at least some period of time. Intumescent materials work well for this purpose, because they swell and char when exposed to flames helping to create a barrier to the fire, heat, and/or smoke.
One particular wall joint with a high potential for allowing fire, heat or smoke to pass from one room to another is the joint between the top of a wall and the ceiling, which can be referred to as a head-of-wall joint. In modern multi-story or multi-level buildings, the head-of-wall joint is often a dynamic joint in which relative movement between the ceiling and the wall is permitted. This relative movement is configured to accommodate deflection in the building due to loading of the ceiling or seismic forces. The conventional method for creating a fire-rated head-of-wall joint is to stuff a fire-resistant mineral wool material into the head-of-wall joint and then spray an elastomeric material over the joint to retain the mineral wool in place. This conventional construction of a fire-rated head-of-wall joint is time-consuming, expensive and has other disadvantages that are described herein.
A wall assembly commonly used in the construction industry includes a header track, bottom track, a plurality of wall studs and a plurality of wall board members, possibly among other components. A typical header track resembles a generally U-shaped (or some other similarly shaped) elongated channel capable of receiving or covering the ends of wall studs and holding the wall studs in place. The header track also permits the wall assembly to be coupled to an upper horizontal support structure, such as a ceiling or floor of a higher level floor of a multi-level building.
Header tracks generally have a web and at least one flange extending from the web. Typically, the header track includes a pair of flanges, which extend in the same direction from opposing edges of the web. The header track can be slotted header track, which includes a plurality of slots spaced along the length of the track and extending in a vertical direction. When the wall studs are placed into the slotted track, each of the plurality of slots accommodates a fastener used to connect the wall stud to the slotted track. The slots allow the wall studs to move generally orthogonally relative to the track. In those areas of the world where earthquakes are common, movement of the wall studs is important. If the wall studs are rigidly attached to the slotted track and not allowed to move freely in at least one direction, the stability of the wall and the building might be compromised. With the plurality of slots, the wall studs are free to move. Even in locations in which earthquakes are not common, movement between the studs and the header track can be desirable to accommodate movement of the building structure due to other loads, such as stationary or moving overhead loads, as described above.
Recently, improved methods of providing a fire-rated head-of-wall joint have been developed. One example of a fire-rated wall construction component is a head-of-wall fire block device sold by the Assignee of the present application under the trademark FireStik®. The FireStik® fire block product incorporates a metal profile with a layer of intumescent material on its inner surface. The metal profile of the FireStik® fire block product is independently and rigidly attached to a structure, such as the bottom of a floor or ceiling, at a position adjacent to the gap between the wallboard (e.g., drywall) and the ceiling on the opposite side (i.e., outside) of the wallboard relative to the studs and header track. The intumescent material, which is adhered to the inner surface of the metal profile, faces the wallboard, stud and header track. The space created in between the wallboard and ceiling, and the space between the stud and header track, allows for independent vertical movement of the stud in the header track when no fire is present.
When temperatures rise, the intumescent material on the FireStik® fire block product expands rapidly and chars. This expansion creates a barrier which fills the head-of-wall gap and inhibits or at least substantially prevents fire, heat and smoke from moving through the head-of-wall joint and entering an adjacent room for at least some period of time.
Still another example of an improved construction component for creating a fire-rated head-of-wall joint is a header track with integrated intumescent material strips sold by the Assignee of the present application under the trademark FAS Track®. In contrast to the FireStik® fire block product, the FAS Track® header track product incorporates the intumescent material directly on the header track so that the fire block material is installed during the framing process. Both the FireStik® and the FAS Track® fire block products are typically installed by the framing crew. The integration of the intumescent material into the FAS Track® header track product eliminates the need to install an additional fire block product after the wall board has been installed, which is typically done by a different crew than the framing crew.